The present invention relates generally to the field of alarm devices and more particularly, is directed to a combination smoke and heat detector alarm system which is equally responsive to either the presence of heat or to the presence of smoke.
The general premise of the need for protecting occupants of buildings from the danger of fire has long been a building design concept and many types of electrically operated and mechanically operated fire alarm systems have been developed by prior workers in the field. The prior art types of fire alarm systems have varied greatly in reliability, complexity, scope, cost and in the basic protection features afforded by each particular type of design. Additionally, distinctions have traditionally been made between alarm systems suitable for commercial and industrial establishments, and in alarm systems particularly designed for residential use.
Alarm systems such as manual fire alarms, automatic fire alarms, central station connected systems, local supervisory alarm systems, coded and non-coded alarm systems, sprinkler alarm systems and others have been developed for particular applications in specified occupancies. It will be appreciated that the initial cost both in basic equipment price and in the cost of installation varies widely between the different systems available. The safety and reliability features offered by the various systems also are widely divergent. Accordingly, the selection and design of an alarm system when planning a new building or when installing an alarm system in an existing building forms an important design decision dependent upon such factors as the type of occupancy, the type of building construction, the number of persons to be protected, the equipment cost factor, etc.
More recently, tests have been conducted and investigations have been made of actual fires wherein it has been determined that in many instances, the buildings subject to fire become untenable from smoke long before they are untenable due to the elevated temperatures of a fire. Because of this added awareness, much thought has been given recently to personnel protection in buildings. In accordance with these recent studies, safety from smoke considerations now form an important building design parameter. Numerous smoke detection devices have been developed to a degree wherein they are quite reliable and are now in general use. The prior art smoke detection systems have, until now, been employed usually to trigger alarm systems in commercial and apartment buildings upon presence of smoke to thereby warn the building occupants. Because of the added awareness of the dangers inherent in residential fires, many self contained, single station, relatively inexpensive units have been specifically design for residential use in an attempt to reduce the number of fatalities resulting from residential fires. Such units have traditionally incorporated a sounding device in the form of a bell or horn and a detecting device which was either responsive to the presence of smoke or to the presence of heat.
There are many reported instances wherein a relatively smoky fire did not generate sufficient heat to actuate a heat-actuated alarm until it was too late to warn the building occupants of the presence of deadly smoke. Other instances have been documented wherein the heat of a fire builds up so quickly as to render a building untenable from heat before sufficient quantities of smoke are generated to activate a usual smoke detection device. Existing smoke detector systems have sometimes failed to properly function when the electrical power required for operation was interrupted by action of the fire itself. Other smoke detector systems have proved deficient to a degree in that the associated alarm device of existing single station units cannot develop sound levels above 93 DBa. Accordingly, a single station unit which incorporates a sounding device capable of emitting alarm signals of greater intensity and which can be actuated both by a heat actuated device and by a smoke actuated device would be most desirable. Heretofore, no such combination unit has been made available for public use.